The BBC have used Silverlight DeepZoom to create a fun site/experience of Radio 1's Big Weekend - even if I was beginning to feel like a stalker at times as I tried it out. Give it a whirl.
DeepZoom allows you to create a composite image with extremely hi-resolution which is streamed to the user as they access different parts of the image at different zoom levels. The Hard Rock Web site also uses the technology, to show off their collection of memorabilia.
This is incredibly easy stuff to develop - check out a 15minute tutorial on using DeepZoom.